Experiments using the spontaneously hypertensive rat (SHR): We will assess the importance of renal metabolism of PGE2 and PGF alpha in the response to or in the genesis of the hypertension in the SHR. We propose to measure renal venous levels of PGE2 and PGF alpha by a sensitive and specific radioimmunoassay. These data will allow us to assess the importance of our in vitro results showing increased renal production of prostaglandins in the SHR. Additionally we propose to evaluate the effects of antihypertensive therapy on renal prostaglandin release. These experiments should permit acceptance or rejection of two conflicting hypotheses regarding the role of renal prostaglandins in experimental hypertension. Tissue culture of renal medullary interstitial cells: We propose to use a line of tissue culture cells which we have derived from rat renal medulla. These in vitro studies will assess the effects of angiotension II on cellular production of PGE2 and PGF. We will also study the role of arachidonic acid substrate and the actions of angiotension II blocking agents. Furthermore the tissue culture system will be used to study the mechanism through which corticosteroids inhibit prostaglandin release by cells.